diff --git a/wolfcrypt/src/asn.c b/wolfcrypt/src/asn.c
index 4f01f5834..cd414329c 100644
--- a/wolfcrypt/src/asn.c
+++ b/wolfcrypt/src/asn.c
@@ -12941,6 +12941,8 @@ static int SetAltNamesFromDcert(Cert* cert, DecodedCert* decoded)
     return ret;
 }
 
+#ifndef NO_FILESYSTEM
+
 /* Set Alt Names from der cert, return 0 on success */
 static int SetAltNamesFromCert(Cert* cert, const byte* der, int derSz)
 {
@@ -12979,6 +12981,8 @@ static int SetAltNamesFromCert(Cert* cert, const byte* der, int derSz)
     return ret < 0 ? ret : 0;
 }
 
+#endif
+
 static int SetDatesFromDcert(Cert* cert, DecodedCert* decoded)
 {
     int ret = 0;